Hello Sapna,
The serial number will be created during order release as per standard SAP functionality.
During confirmation you can make an enhancement in the system to print the serial number label.
We also had a similar issue and we solved it by creating a custom transaction, in which you enter the production order number and the transaction shows you all the serial numbers against it. Then user has the option to select any 1 serial number or many and print the serial number label.
It is not a good idea to increase production order quantity just to print a serial number label.
Best Regards,
Ameya B.